An apparatus and method for intra-predicting an image are provided. The method includes: obtaining, based on restored neighboring pixels of a chrominance block and restored neighboring pixels of a luminance pixel corresponding to the chrominance block, parameters representing a correlation between the chrominance block that is to be intra-predicted and a luminance block; and predicting, using the parameters, the chrominance block from the luminance block, wherein the obtaining the parameters includes performing a predetermined operation on the restored neighboring pixels of the chrominance block and the restored neighboring pixels of the luminance block, and wherein the predetermined operation comprises an adaptive scaling process of changing bit depths of the parameters to reduce a size of a look-up table and prevent an occurrence of overflow.

Encoding efficiency for attribute information in point cloud information is improved. A point cloud encoding device includes a subsampling unit configured to preserve chroma signals of some points in a point cloud to be encoded and discard chroma signals of remaining points other than those points, and an attribute information encoding unit configured to encode the chroma signals of those points in the point cloud to be encoded and luma signals of all points.